It is said that twenty to twenty-five percentages of energy consumed at an entire plant correspond to total energy consumed by gas compressors such as an air compressor, and it is greatly effective to recover waste heat from the gas compressor. Especially, for the purpose of achieving an object of reducing an amount of CO2 emission starting from global heating, use of the waste-heat from the gas compressor is expected to be further given importance in future.
The gas compressor is composed of: a compressor body compressing gas such as air; a cooling system absorbing heat generated by compression; a motor as a source of drive power; etc. Moreover, in the gas compressor, where motor input power is 100%, the amount of heat absorbed in the cooling system corresponds to 90% or more thereof, this amount of heat is usually released to outside air, and a great deal of energy is discharged to the air. To reduce the amount of waste heat, achievement of higher efficiency of the compressor body and the motor has been promoted, but its effect is several percentages at a maximum, which therefore raises demands for effective use of the waste heat from the gas compressor.
For the effective use of the waste heat from the gas compressor, cases include: use for air heating, warm water use, and use for boiler feed-water preheat, which are still under study.
Described as this type of conventional art is, for example, Japanese Patent No. 4329875 (Patent Document 1). In this Patent Document 1, a compressor is driven by using vapor, and heat generated at the compressor is used for preheat of water (feed-water) supplied to a boiler, thereby reducing energy consumed at the boiler.